Display device is one of the most common input or output electronic devices. Display device is configured to display text, images, and videos.
Contemporary display device usually has a wide viewing angle screen. Its visible angle of view can be as wide as from approximately 120 to 170 degree. When users use these devices in bus, subway, or other crowded public places, the content on the screen can be easily exposed and visible to other people around, which may lead to serious privacy leaks.